Known systems for providing scheduled zone audio for school bells, factory bells, and other applications require the use of proprietary devices and cabling. The most common existing systems use electronic timers to schedule the activation of relays at scheduled times. The timers activate a relay at scheduled times which completes a circuit and allows power to be sent through to electronic bell devices. There are several disadvantages to this solution. First, the electronic timers are very difficult to program and require a technician with special training to program the schedules. Second, the system only allows a single bell or tone sound to be played. Users cannot select different tones or bell sounds to signify different events, such as a class warning bell and a class tardy bell. In addition, since the bell circuits are hardwired, all devices on the circuit must play when triggered by the relay. There is no capability to trigger an individual device with the electronic time, unless a separate circuit is created for each bell device. Finally, the system requires a timer device in each location where bell circuits are located and the schedules must be maintained separately on each timer device. Different timers are likely to lose synchronization, so bell events that are intended to play at the same time on different timers may play at different times.
Another existing system uses a paging amplifier attached to an electronic timer and a chime device. The paging amplifier in this system includes contact closures that activate zones on the paging amplifier. The contact closures are wired through the electronic timer for each zone. When the electronic timer activates a relay, it completes the contact closure circuit which selects the zone on the paging amplifier. The chime device plays a selected sound according to how the chime device is wired. This system has similar disadvantages to the first system. The electronic timer requires a specialist to program the timer. The system can only play the selected chime sound from the chime device. In addition, all devices on the zone output of the amplifier must play audio when triggered by the timer. It is not possible to send audio to a specific speaker or audio device, unless a separate cable is ran to the amplifier for each device. The timer for each paging amplifier must also be programmed and maintained separately. This may also lead to timers becoming unsynchronized, which will result in bells playing at different times than expected.